NTE8255 NTE Electronics, Inc., NTE8255 Datasheet - Page 5

• Manufacturer Part Number: NTE8255
• Description: Integrated Circuit Programmable Peripheral Interface
• Manufacturer: NTE Electronics, Inc.

Functional Description (Cont’d):
Group I and Group II Controls
Through an OUT instruction in System Software from the processor, a control word is transmitted to
the NTE8255. Information such as “MODE”, “Bit SET”, and “Bit RESET” is used to initialize the func-
tional configuration of each I/O port.
Each group (I and II) accepts “commands” from the Read/Write Control Logic and “control words” from
the internal data bus and in turn controls its associated I/O ports.
While the Control Word Register can be written into, the contents cannot be read back to the processor.
Ports A, B, and C
The three 8−bit I/O ports (A, B, and C) in the NTE8255 can all be configured to meet a wide variety
of functional requirements through system software. The effectiveness and flexibility of the NTE8255
are further enhanced by special features unique to each of the ports.
Port C may be divided into two independent 4−bit control and status ports for use with Ports A and B.
Group I − Port A and upper Port C (PC
Group II − Port B and lower Port C (PC
Port A
Port B
Port C
= An 8−bit data output latch/buffer and data input latch.
= An 8−bit data input/output latch/buffer and an 8−bit data input buffer.
= An 8−bit output latch/buffer and a data input buffer (input not latched).
GND
PC7
PC6
PC5
PC4
PC0
PC1
PC2
PC3
PB0
PB1
PB2
PA3
PA2
PA1
PA0
RD
CS
A1
A0
Pin Connection Diagram
10
11
12
13
14
15
16
17
18
19
20
1
2
3
4
5
6
7
8
9
3
7
− PC
− PC
40
39
38
37
36
35
34
33
32
31
30
29
28
27
26
25
24
23
22
21
PA4
PA5
PA6
PA7
WR
RESET
D0
D1
D2
D3
D4
D5
D6
D7
V
PB7
PB6
PB5
PB4
PB3
0
4
CC
)
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